Cross Networking Speakers

[MTGKING]

I have 2x Sony 6 ohm 30-60W woofers, a LG 8 ohm 35W woofer, and 2x Unbranded 4 ohm 3W tweeters. I've had the drivers laying around for awhile, and can't stand having them go to waste any longer. The plan is to make a custom enclosure that keeps them all divided, but the problem is that I don't know the best way to wire them to get the most power. I've always heard to never mix sub sizes, but I don't want to buy three different amps just to run them. What is the best way to run all of these at the same time with a single amp? Any suggestions are very much appreciated.

[MTGKING]

I should probably mention that this is for a home entertainment system, and not for a car. 

[anothertom]

I'm going to make this perfectly clear before I go any further. Unless you have a good understanding of electrical engineering and a very good understanding of speaker design you shouldn't even bother attempting this and expecting a good result. The fact you're asking this question means you probably shouldn't waste your time on it.*

 

The question you're basically asking is, how do i get the right frequencies to the right drivers? to which there are sort of three answers.

 

1) Full range drivers.

2) Passive crossover circuit.

3) Active Crossover / Signal processing

 

The first option is (hopefully) obvious as to how it works. Send a full range signal from the source to the amp to the speaker with direct connection to the driver.

 

The third option uses a signal processor/router (e.g. the classic soundweb 9088ii) which uses various mathematical functions (Fourier transforms etc...) to separate different frequency ranges, apply compression/limiters/delay and to output the required number of signals. Each signal would be amplified separately and sent to the intended driver.

 

For a quick example, a PA system might consist of a mid-top cabinet and a sub per side. The mid-top has a compression driver (or tweeter to use the consumer term) and a mid range driver, the sub has a single 18" driver. the stereo signal will be split into a HI, MID and SUB signal for each side (left and right) in the processor, which will output six different signals. Three 2 channel amps will run each pair of drivers each rated to a suitable wattage for the driver. outputs from the amps will be directly connected to the drivers.

 

But what you're asking about is the second option, a passive crossover circuit. This is a circuit which uses a series of capacitors, resistors and inductors to create Hi-pass filters, low-pass filters, impedance levelling, and specific filters to separate an incoming signal into multiple signals suitable for the different drivers in a speaker. This is what is used in HiFi speakers and some professional PA systems.

 

confession time: I don't know enough about speaker design or crossover design to have written this without some emergency research.

 

Crossovers can be as simple as adding a single capacitor and a single inductor to a speaker circuit, but if your drivers have different sensitivities then levelling pads can compensate for this. This Guide goes step by step through the design process of a crossover for a 3-way speaker, and shows even more options to consider.

 

'Cool' you're thinking 'I can follow that guide, and use the calculators linked to design the bestest possible crossover for my speakers. What's this guy talking about when he says it can be difficult...'

 

So what frequency do you want your woofers to cross over at? How low will the tweeter run? How high will it run? what are their resonant frequencies? what is their frequency response over a wide range? Do you want the two woofers to overlap? But most importantly, how do you know this? spec sheets can be helpful, but for resonance you'll need to use impulse tests, and as for the crossover frequency, which you'll be guessing, what if you get that wrong and it sounds rubbish? back to the start with you...

 

This is where the active signal processing can be more forgiving. You can slowly tune a system until it sounds right, you don't have to pull everything apart just because you overestimated something or forgot to take into account the difference between theory and the real world.

 

I don't mean to discourage you from learning, and there is a lot of useful information out there on the interwebs. But maybe start smaller than a 3-way crossover.

 

As for speaker design, well... all speaker manufacturers will be running CFD calculations on their designs, then tweaking them, then more CFD, then tweak the design again... you won't have that luxury.

 

By all means build a box and surface mount the drivers, but i wouldn't expect it to sound as good as anything you could buy for $20 or less.

 

What may be more rewarding for you is to find a good DIY speaker and build that instead, as everything about it will be better than what you can do on your own, especially with 2 sony drivers, 1 LG driver and unbranded tweeters.

[MTGKING]

21 minutes ago, anothertom said:

I'm going to make this perfectly clear before I go any further. Unless you have a good understanding of electrical engineering and a very good understanding of speaker design you shouldn't even bother attempting this and expecting a good result. The fact you're asking this question means you probably shouldn't waste your time on it.*

 

The question you're basically asking is, how do i get the right frequencies to the right drivers? to which there are sort of three answers.

 

1) Full range drivers.

2) Passive crossover circuit.

3) Active Crossover / Signal processing

 

The first option is (hopefully) obvious as to how it works. Send a full range signal from the source to the amp to the speaker with direct connection to the driver.

 

The third option uses a signal processor/router (e.g. the classic soundweb 9088ii) which uses various mathematical functions (Fourier transforms etc...) to separate different frequency ranges, apply compression/limiters/delay and to output the required number of signals. Each signal would be amplified separately and sent to the intended driver.

 

For a quick example, a PA system might consist of a mid-top cabinet and a sub per side. The mid-top has a compression driver (or tweeter to use the consumer term) and a mid range driver, the sub has a single 18" driver. the stereo signal will be split into a HI, MID and SUB signal for each side (left and right) in the processor, which will output six different signals. Three 2 channel amps will run each pair of drivers each rated to a suitable wattage for the driver. outputs from the amps will be directly connected to the drivers.

 

But what you're asking about is the second option, a passive crossover circuit. This is a circuit which uses a series of capacitors, resistors and inductors to create Hi-pass filters, low-pass filters, impedance levelling, and specific filters to separate an incoming signal into multiple signals suitable for the different drivers in a speaker. This is what is used in HiFi speakers and some professional PA systems.

 

confession time: I don't know enough about speaker design or crossover design to have written this without some emergency research.

 

Crossovers can be as simple as adding a single capacitor and a single inductor to a speaker circuit, but if your drivers have different sensitivities then levelling pads can compensate for this. This Guide goes step by step through the design process of a crossover for a 3-way speaker, and shows even more options to consider.

 

'Cool' you're thinking 'I can follow that guide, and use the calculators linked to design the bestest possible crossover for my speakers. What's this guy talking about when he says it can be difficult...'

 

So what frequency do you want your woofers to cross over at? How low will the tweeter run? How high will it run? what are their resonant frequencies? what is their frequency response over a wide range? Do you want the two woofers to overlap? But most importantly, how do you know this? spec sheets can be helpful, but for resonance you'll need to use impulse tests, and as for the crossover frequency, which you'll be guessing, what if you get that wrong and it sounds rubbish? back to the start with you...

 

This is where the active signal processing can be more forgiving. You can slowly tune a system until it sounds right, you don't have to pull everything apart just because you overestimated something or forgot to take into account the difference between theory and the real world.

 

I don't mean to discourage you from learning, and there is a lot of useful information out there on the interwebs. But maybe start smaller than a 3-way crossover.

 

As for speaker design, well... all speaker manufacturers will be running CFD calculations on their designs, then tweaking them, then more CFD, then tweak the design again... you won't have that luxury.

 

By all means build a box and surface mount the drivers, but i wouldn't expect it to sound as good as anything you could buy for $20 or less.

 

What may be more rewarding for you is to find a good DIY speaker and build that instead, as everything about it will be better than what you can do on your own, especially with 2 sony drivers, 1 LG driver and unbranded tweeters.

This may be the most helpful response I have gotten from anybody on a forum ever!

I am definitely not an electrician, so even though what you said makes sense, I'll take your advice so I don't end up with a speaker system that sounds like a Russet potato killing Mariah Carey.

My only question is, could I get a quad channel amp, give each type of sub its own channel, and then just limit the output to each?

[anothertom]

15 minutes ago, MTGKING said:

My only question is, could I get a quad channel amp, give each type of sub its own channel, and then just limit the output to each?

Yes, you can easily hook up each driver to its own amp channel without causing issues to the amp. But limiting each channel would depend on how clever the amplifier is. A fully analog amp won't be able to limit anything outside not turning it up all the way. An amp with some processing would allow a hard limit to be set, but the cost of such a model puts it out of the hobbyist range.